Effect of pyrolysis conditions on levoglucosan yield from cotton straw and optimization of levoglucosan extraction from bio-oil

Abstract

Fast pyrolysis of cotton straw was performed under different temperature ranges, particle sizes, holding times and acid concentrations in a fluidized bed reactor to maximize the yield of levoglucosan (LG). The maximum LG yield was obtained at the optimal pyrolytic conditions: temperature of 500°C, holding time of 1.4s, particle size of 600–650μm and acid concentration of 8%. Furthermore, an improved method to quickly and easily extract LG from bio-oil was developed by utilizing precipitation and Soxhlet extraction to quantitatively remove organic colloid, pigments and aromatic compounds with less loss of LG during extraction. The process was optimized by using Box-Behnken design for three reaction parameters: the volume of water (A), the quality of activiaed carbon (B), and pH (C). The extraction presented required no prolonged high heating (thus protecting the LG from hydrolysis), used benign reagents, and realized a significant purity over other methods. The purity and structure of LG were determined by busing chromatographic and spectroscopic techniques, such as HPLC, FT-IR and NMR spectroscopy. The optimal extraction yield of LG from the straw bio-oil was 78% with the purity of 95.56%. This research also applied a new method to quickly determine the quantitative and qualitative analysis test parameters of LG.